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Evolution of Life
Life Began on Earth between 4500 Mya and 2500 Mya probably due to Self-Replicating Molecules (Probably RNA) converting in to Proto-Cells. Earliest Animals The earliest animals evolved in the Neoproterozoic Ediacaran One of the earliest confirmed animals was known as Xenusion a primitive worm or panarthropod. These evolved eventually in to early Panarthropod groups such as Anomalocaridids in the and Trilobites and (eventually) giving rise to the first backboned animals. First Vertebrates A vertebrate is an animal with a backbone the first vertebrates were early Fish in the Cambrian seas Cambrian During the Cambrian there was no life on the land and the seas were ruled by invertebrates such as Anomalocaris of the Anomalocaridids and the five eyed Opabinia. However in these waters there also lived early fish such as Pikaia and Haikouichthys. The Evolution of Fish After first evolving in the Cambrian they didn't rule the oceans until the Devonian instead the Ordovician and Silurian periods were ruled by Sea Scorpions or Eurypterids Ordovician During the Ordovician animals made their first tentative steps onto land Eurypterids like Megalograptus walked onto land to spawn. The seas were ruled by the Orthocones giant squid like animals such as Cameroceras and Orthoceras. Fish continued to evolve as armored fish the first true fish Arandaspis evolved around this time with its cousins Astraspis and Sacabambaspis also Trilobites continued to exist. Ordovician-Silurian extinction The Ordovician-Silurian Extinction was a catastrophic loss of life at the boundary between those periods. 49% of Animals died out including many Brachiopods and Trilobites. As a result of this the beginning of the Silurian was irradiated. Silurian After the extinction the biodiversity of earth was significantly damaged but Fish and Eurypterids continued to evolve the Eurypterids evolving into insects and arachnids (Brontoscorpio) fish such as Procephalaspis swam the seas The firstSharks such as Elegestolepis, Mongolepis and Polymerolepis. Age of Fishes The Time when fish really began to rule the seas Devonian Often Known as the age of Fishes Vertebrates The Devonian while being termed the Age of Fishes also saw the beginning of primitive amphibians such as Hynerpeton whilst Sharks still existed (Stethacanthus they were dwarfed by armored fish such as Dunkleosteus = Selected Genera = *Hynerpeton *Hyneria *Stethacanthus = Placoderms = These Superb armored Fish ruled the Devonian seas covered in armour they were unchallenged in every aspect of Devonian marine life but despite this in the end they all went extinct leaving no present day relatives. Selected Genera *Dunkleosteus *Bothriolepis Invertebrates Arachnids first colonised the land scorpions such as Eoscorpius were amongst the first animals to colonise the land. In the sea the last of the Anomalocaridids Schinderhannes still lived along with some Eurypterids. Moving on to land From the Carboniferous animals moved on to land Carboniferous The Carboniferous saw the rise of giant insects. Insects Due to there being a considerable amount more Oxygen in the atmosphere during the Carboniferous; Insects could grow much larger. The giant dragonfly Meganeura was perhaps the largest of all flying invertebrates. Selected Genera *Meganeura Amphibians Amphibians continued to evolve some such as Proterogyrinus could now travel much further away from water as they became the very first reptiles. Selected Genera *Proterogyrinus *Crassigyrinus Reptiles The First reptiles evolved during this time, early ones such as Spinoaequalis were similar in size and appearance to modern day lizards Selected Genera *Petrolacosaurus *Spinoaequalis Fish Fish continued on sharks ruled the seas Arachnids As with insects Arachnids grew much larger scorpions such as Pulmonoscorpius were some of the largest ever seen. Selected Genera *Pulmonoscorpius *Protosolpuga Centipedes and Millipedes Like the arachnids and insects centipedes and millipedes continued and Arthropleura was the biggest arthropod of all time. Rulers of the Land From the Permian onwards the animals ruled unquestionably Permian During the Permian most of the planet was ruled by Synapsids or mammal like reptiles Synapsids The Synapsids were divided into 2 groups the Therapsids and Pelycosaurs. Therapsids These were the most sucessful during the permian with the Gorgonopsids such as Inostrancevia and the Dicynodonts like Diictodon being the most common animals around at that time Pelycosaurs The Pelycosaurs were less mammal like than the therapsids and less sucessful. The Iconic Dimetrodon was a Pelycosaur. Invertebrates The Desert like atmosphere of the Permian made it hard for land invetebrates though one Meganeuropsis may be the largest dragonfly that ever lived.